Linkage maps in cucumber have been constructed in broad and narrow genetic base populations, using mostly RFLPs. RAPD markers are believed to be more advantageous than RFLPs for mapping in narrow crosses. An F3 population derived from F2 intercrossing cucumber inbred lines (G421 and H19) was used to construct a linkage map and to perform QTL analysis for horticultural traits recorded in two locations. One hundred three F3 families were used for mapping purpose. The parents were screened using ≈1500 primers yielding 80 RAPD markers that exhibited expected 3:1 Mendelian segregation. Additionally, female sex expression (F), little leaf (l), and determinate (de) loci also were evaluated in the segregating population. The linkage analysis and mapping was performed with MAPMAKER software, using a LOD score of 3.0 and recombination frequency of 0.40. QTL analysis was performed using one-way analysis of variance (ANOVA) and MAPMAKER/QTL. The linkage map integrates 83 map-points assembled into nine linkage groups. F and de loci mapped to linkage group `B', and the l locus was placed on linkage group `D'. The total map length is 628 cM, with an average distance between loci of 8.4 cM. Results from using one-way ANOVA and MAPMAKER/QTL had a good agreement for most QTL detected. Some QTL were location specific. Across locations four, one and three QTL were detected for sex expression, mainstem length, and number of laterals, respectively.
Felix C. Serquen, J. Bacher, and J. Staub
Jack E. Staub, Felix C. Serquen, and Manju Gupta
Felix C. Serquen, Jeff Bacher, and Jack E. Staub
Plant architecture can be manipulated in cucumber (Cucumis sativus L.) to provide an array of phenotypes. Determinate, multiple-lateral plants are unique because they afford an opportunity to increase fruit yield per plant. Estimates of genetic variances, numbers of genetic factors, and genotypic and phenotypic correlations between traits were made in a population, segregating for sex expression, leaf size, and plant habit at low plant density (≈19,000 plants/ha). Replicated evaluation of 100 F3 families derived from an initial mating between a gynoecious, determinate, moderately branched line (G421) and a monoecious, indeterminate, multiple lateral branching line (`H-19') indicated that mainstem length and multiple lateral branching exhibit mostly additive genetic variance. For sex expression, additive and dominant genetic variances were important. The minimum number of genetic factors controlling sex expression, number of lateral branches, and mainstem length were estimated at five, four, and eight, respectively. Phenotypic and genotypic correlations between traits indicated that relative leaf size may influence fruit mass while having only limited influence on the number of fruit produced per plant. The amount and type of genetic variation suggests that the development of an array of determinate, multiple-lateral branching plant types with varying sex expression and plant stature is possible.